
<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <meta charset="utf-8" />
    <title>Type Objects &#8212; Python 3.8.13 documentation</title><meta name="viewport" content="width=device-width, initial-scale=1.0">
    
    <link rel="stylesheet" href="../_static/pydoctheme.css?2022.1" type="text/css" />
    <link rel="stylesheet" href="../_static/pygments.css" type="text/css" />
    
    <script id="documentation_options" data-url_root="../" src="../_static/documentation_options.js"></script>
    <script src="../_static/jquery.js"></script>
    <script src="../_static/underscore.js"></script>
    <script src="../_static/doctools.js"></script>
    <script src="../_static/language_data.js"></script>
    
    <script src="../_static/sidebar.js"></script>
    
    <link rel="search" type="application/opensearchdescription+xml"
          title="Search within Python 3.8.13 documentation"
          href="../_static/opensearch.xml"/>
    <link rel="author" title="About these documents" href="../about.html" />
    <link rel="index" title="Index" href="../genindex.html" />
    <link rel="search" title="Search" href="../search.html" />
    <link rel="copyright" title="Copyright" href="../copyright.html" />
    <link rel="next" title="The None Object" href="none.html" />
    <link rel="prev" title="Concrete Objects Layer" href="concrete.html" />
    <link rel="canonical" href="https://docs.python.org/3/c-api/type.html" />
    
      
    

    
    <style>
      @media only screen {
        table.full-width-table {
            width: 100%;
        }
      }
    </style>
<link rel="shortcut icon" type="image/png" href="../_static/py.svg" />
            <script type="text/javascript" src="../_static/copybutton.js"></script>
            <script type="text/javascript" src="../_static/menu.js"></script> 

  </head>
<body>
<div class="mobile-nav">
    <input type="checkbox" id="menuToggler" class="toggler__input" aria-controls="navigation"
           aria-pressed="false" aria-expanded="false" role="button" aria-label="Menu" />
    <label for="menuToggler" class="toggler__label">
        <span></span>
    </label>
    <nav class="nav-content" role="navigation">
         <a href="https://www.python.org/" class="nav-logo">
             <img src="../_static/py.svg" alt="Logo"/>
         </a>
        <div class="version_switcher_placeholder"></div>
        <form role="search" class="search" action="../search.html" method="get">
            <svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 24 24" class="search-icon">
                <path fill-rule="nonzero"
                        d="M15.5 14h-.79l-.28-.27a6.5 6.5 0 001.48-5.34c-.47-2.78-2.79-5-5.59-5.34a6.505 6.505 0 00-7.27 7.27c.34 2.8 2.56 5.12 5.34 5.59a6.5 6.5 0 005.34-1.48l.27.28v.79l4.25 4.25c.41.41 1.08.41 1.49 0 .41-.41.41-1.08 0-1.49L15.5 14zm-6 0C7.01 14 5 11.99 5 9.5S7.01 5 9.5 5 14 7.01 14 9.5 11.99 14 9.5 14z" fill="#444"></path>
            </svg>
            <input type="text" name="q" aria-label="Quick search"/>
            <input type="submit" value="Go"/>
        </form>
    </nav>
    <div class="menu-wrapper">
        <nav class="menu" role="navigation" aria-label="main navigation">
            <div class="language_switcher_placeholder"></div>
  <h3><a href="../contents.html">Table of Contents</a></h3>
  <ul>
<li><a class="reference internal" href="#">Type Objects</a><ul>
<li><a class="reference internal" href="#creating-heap-allocated-types">Creating Heap-Allocated Types</a></li>
</ul>
</li>
</ul>

  <h4>Previous topic</h4>
  <p class="topless"><a href="concrete.html"
                        title="previous chapter">Concrete Objects Layer</a></p>
  <h4>Next topic</h4>
  <p class="topless"><a href="none.html"
                        title="next chapter">The <code class="docutils literal notranslate"><span class="pre">None</span></code> Object</a></p>
  <div role="note" aria-label="source link">
    <h3>This Page</h3>
    <ul class="this-page-menu">
      <li><a href="../bugs.html">Report a Bug</a></li>
      <li>
        <a href="https://github.com/python/cpython/blob/3.8/Doc/c-api/type.rst"
            rel="nofollow">Show Source
        </a>
      </li>
    </ul>
  </div>
        </nav>
    </div>
</div>

  
    <div class="related" role="navigation" aria-label="related navigation">
      <h3>Navigation</h3>
      <ul>
        <li class="right" style="margin-right: 10px">
          <a href="../genindex.html" title="General Index"
             accesskey="I">index</a></li>
        <li class="right" >
          <a href="../py-modindex.html" title="Python Module Index"
             >modules</a> |</li>
        <li class="right" >
          <a href="none.html" title="The None Object"
             accesskey="N">next</a> |</li>
        <li class="right" >
          <a href="concrete.html" title="Concrete Objects Layer"
             accesskey="P">previous</a> |</li>

          <li><img src="../_static/py.svg" alt="python logo" style="vertical-align: middle; margin-top: -1px"/></li>
          <li><a href="https://www.python.org/">Python</a> &#187;</li>
          <li class="switchers">
            <div class="language_switcher_placeholder"></div>
            <div class="version_switcher_placeholder"></div>
          </li>
          <li>
              
          </li>
    <li id="cpython-language-and-version">
      <a href="../index.html">3.8.13 Documentation</a> &#187;
    </li>

          <li class="nav-item nav-item-1"><a href="index.html" >Python/C API Reference Manual</a> &#187;</li>
          <li class="nav-item nav-item-2"><a href="concrete.html" accesskey="U">Concrete Objects Layer</a> &#187;</li>
                <li class="right">
                    

    <div class="inline-search" role="search">
        <form class="inline-search" action="../search.html" method="get">
          <input placeholder="Quick search" aria-label="Quick search" type="text" name="q" />
          <input type="submit" value="Go" />
          <input type="hidden" name="check_keywords" value="yes" />
          <input type="hidden" name="area" value="default" />
        </form>
    </div>
                     |
                </li>
            
      </ul>
    </div>    

    <div class="document">
      <div class="documentwrapper">
        <div class="bodywrapper">
          <div class="body" role="main">
            
  <div class="section" id="type-objects">
<span id="typeobjects"></span><h1>Type Objects<a class="headerlink" href="#type-objects" title="Permalink to this headline">¶</a></h1>
<span class="target" id="index-0"></span><dl class="type">
<dt id="c.PyTypeObject">
<code class="sig-name descname">PyTypeObject</code><a class="headerlink" href="#c.PyTypeObject" title="Permalink to this definition">¶</a></dt>
<dd><p>The C structure of the objects used to describe built-in types.</p>
</dd></dl>

<dl class="var">
<dt id="c.PyType_Type">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PyType_Type</code><a class="headerlink" href="#c.PyType_Type" title="Permalink to this definition">¶</a></dt>
<dd><p>This is the type object for type objects; it is the same object as
<a class="reference internal" href="../library/functions.html#type" title="type"><code class="xref py py-class docutils literal notranslate"><span class="pre">type</span></code></a> in the Python layer.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyType_Check">
int <code class="sig-name descname">PyType_Check</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyType_Check" title="Permalink to this definition">¶</a></dt>
<dd><p>Return true if the object <em>o</em> is a type object, including instances of types
derived from the standard type object.  Return false in all other cases.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyType_CheckExact">
int <code class="sig-name descname">PyType_CheckExact</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyType_CheckExact" title="Permalink to this definition">¶</a></dt>
<dd><p>Return true if the object <em>o</em> is a type object, but not a subtype of the
standard type object.  Return false in all other cases.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyType_ClearCache">
unsigned int <code class="sig-name descname">PyType_ClearCache</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyType_ClearCache" title="Permalink to this definition">¶</a></dt>
<dd><p>Clear the internal lookup cache. Return the current version tag.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyType_GetFlags">
unsigned long <code class="sig-name descname">PyType_GetFlags</code><span class="sig-paren">(</span><a class="reference internal" href="#c.PyTypeObject" title="PyTypeObject">PyTypeObject</a>*<em> type</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyType_GetFlags" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the <a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_flags" title="PyTypeObject.tp_flags"><code class="xref c c-member docutils literal notranslate"><span class="pre">tp_flags</span></code></a> member of <em>type</em>. This function is primarily
meant for use with <cite>Py_LIMITED_API</cite>; the individual flag bits are
guaranteed to be stable across Python releases, but access to
<a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_flags" title="PyTypeObject.tp_flags"><code class="xref c c-member docutils literal notranslate"><span class="pre">tp_flags</span></code></a> itself is not part of the limited API.</p>
<div class="versionadded">
<p><span class="versionmodified added">New in version 3.2.</span></p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.4: </span>The return type is now <code class="docutils literal notranslate"><span class="pre">unsigned</span> <span class="pre">long</span></code> rather than <code class="docutils literal notranslate"><span class="pre">long</span></code>.</p>
</div>
</dd></dl>

<dl class="function">
<dt id="c.PyType_Modified">
void <code class="sig-name descname">PyType_Modified</code><span class="sig-paren">(</span><a class="reference internal" href="#c.PyTypeObject" title="PyTypeObject">PyTypeObject</a><em> *type</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyType_Modified" title="Permalink to this definition">¶</a></dt>
<dd><p>Invalidate the internal lookup cache for the type and all of its
subtypes.  This function must be called after any manual
modification of the attributes or base classes of the type.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyType_HasFeature">
int <code class="sig-name descname">PyType_HasFeature</code><span class="sig-paren">(</span><a class="reference internal" href="#c.PyTypeObject" title="PyTypeObject">PyTypeObject</a><em> *o</em>, int<em> feature</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyType_HasFeature" title="Permalink to this definition">¶</a></dt>
<dd><p>Return true if the type object <em>o</em> sets the feature <em>feature</em>.  Type features
are denoted by single bit flags.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyType_IS_GC">
int <code class="sig-name descname">PyType_IS_GC</code><span class="sig-paren">(</span><a class="reference internal" href="#c.PyTypeObject" title="PyTypeObject">PyTypeObject</a><em> *o</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyType_IS_GC" title="Permalink to this definition">¶</a></dt>
<dd><p>Return true if the type object includes support for the cycle detector; this
tests the type flag <a class="reference internal" href="typeobj.html#Py_TPFLAGS_HAVE_GC" title="Py_TPFLAGS_HAVE_GC"><code class="xref py py-const docutils literal notranslate"><span class="pre">Py_TPFLAGS_HAVE_GC</span></code></a>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyType_IsSubtype">
int <code class="sig-name descname">PyType_IsSubtype</code><span class="sig-paren">(</span><a class="reference internal" href="#c.PyTypeObject" title="PyTypeObject">PyTypeObject</a><em> *a</em>, <a class="reference internal" href="#c.PyTypeObject" title="PyTypeObject">PyTypeObject</a><em> *b</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyType_IsSubtype" title="Permalink to this definition">¶</a></dt>
<dd><p>Return true if <em>a</em> is a subtype of <em>b</em>.</p>
<p>This function only checks for actual subtypes, which means that
<a class="reference internal" href="../reference/datamodel.html#class.__subclasscheck__" title="class.__subclasscheck__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__subclasscheck__()</span></code></a> is not called on <em>b</em>.  Call
<a class="reference internal" href="object.html#c.PyObject_IsSubclass" title="PyObject_IsSubclass"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyObject_IsSubclass()</span></code></a> to do the same check that <a class="reference internal" href="../library/functions.html#issubclass" title="issubclass"><code class="xref py py-func docutils literal notranslate"><span class="pre">issubclass()</span></code></a>
would do.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyType_GenericAlloc">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PyType_GenericAlloc</code><span class="sig-paren">(</span><a class="reference internal" href="#c.PyTypeObject" title="PyTypeObject">PyTypeObject</a><em> *type</em>, Py_ssize_t<em> nitems</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyType_GenericAlloc" title="Permalink to this definition">¶</a></dt>
<dd><em class="refcount">Return value: New reference.</em><p>Generic handler for the <a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_alloc" title="PyTypeObject.tp_alloc"><code class="xref c c-member docutils literal notranslate"><span class="pre">tp_alloc</span></code></a> slot of a type object.  Use
Python’s default memory allocation mechanism to allocate a new instance and
initialize all its contents to <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyType_GenericNew">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PyType_GenericNew</code><span class="sig-paren">(</span><a class="reference internal" href="#c.PyTypeObject" title="PyTypeObject">PyTypeObject</a><em> *type</em>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *args</em>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *kwds</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyType_GenericNew" title="Permalink to this definition">¶</a></dt>
<dd><em class="refcount">Return value: New reference.</em><p>Generic handler for the <a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_new" title="PyTypeObject.tp_new"><code class="xref c c-member docutils literal notranslate"><span class="pre">tp_new</span></code></a> slot of a type object.  Create a
new instance using the type’s <a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_alloc" title="PyTypeObject.tp_alloc"><code class="xref c c-member docutils literal notranslate"><span class="pre">tp_alloc</span></code></a> slot.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyType_Ready">
int <code class="sig-name descname">PyType_Ready</code><span class="sig-paren">(</span><a class="reference internal" href="#c.PyTypeObject" title="PyTypeObject">PyTypeObject</a><em> *type</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyType_Ready" title="Permalink to this definition">¶</a></dt>
<dd><p>Finalize a type object.  This should be called on all type objects to finish
their initialization.  This function is responsible for adding inherited slots
from a type’s base class.  Return <code class="docutils literal notranslate"><span class="pre">0</span></code> on success, or return <code class="docutils literal notranslate"><span class="pre">-1</span></code> and sets an
exception on error.</p>
</dd></dl>

<dl class="function">
<dt id="c.PyType_GetSlot">
void* <code class="sig-name descname">PyType_GetSlot</code><span class="sig-paren">(</span><a class="reference internal" href="#c.PyTypeObject" title="PyTypeObject">PyTypeObject</a><em> *type</em>, int<em> slot</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyType_GetSlot" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the function pointer stored in the given slot. If the
result is <code class="docutils literal notranslate"><span class="pre">NULL</span></code>, this indicates that either the slot is <code class="docutils literal notranslate"><span class="pre">NULL</span></code>,
or that the function was called with invalid parameters.
Callers will typically cast the result pointer into the appropriate
function type.</p>
<p>See <code class="xref c c-member docutils literal notranslate"><span class="pre">PyType_Slot.slot</span></code> for possible values of the <em>slot</em> argument.</p>
<p>An exception is raised if <em>type</em> is not a heap type.</p>
<div class="versionadded">
<p><span class="versionmodified added">New in version 3.4.</span></p>
</div>
</dd></dl>

<div class="section" id="creating-heap-allocated-types">
<h2>Creating Heap-Allocated Types<a class="headerlink" href="#creating-heap-allocated-types" title="Permalink to this headline">¶</a></h2>
<p>The following functions and structs are used to create
<a class="reference internal" href="typeobj.html#heap-types"><span class="std std-ref">heap types</span></a>.</p>
<dl class="function">
<dt id="c.PyType_FromSpecWithBases">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PyType_FromSpecWithBases</code><span class="sig-paren">(</span><a class="reference internal" href="#c.PyType_Spec" title="PyType_Spec">PyType_Spec</a><em> *spec</em>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *bases</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyType_FromSpecWithBases" title="Permalink to this definition">¶</a></dt>
<dd><em class="refcount">Return value: New reference.</em><p>Creates and returns a heap type object from the <em>spec</em>
(<a class="reference internal" href="typeobj.html#Py_TPFLAGS_HEAPTYPE" title="Py_TPFLAGS_HEAPTYPE"><code class="xref py py-const docutils literal notranslate"><span class="pre">Py_TPFLAGS_HEAPTYPE</span></code></a>).</p>
<p>If <em>bases</em> is a tuple, the created heap type contains all types contained
in it as base types.</p>
<p>If <em>bases</em> is <code class="docutils literal notranslate"><span class="pre">NULL</span></code>, the <em>Py_tp_bases</em> slot is used instead.
If that also is <code class="docutils literal notranslate"><span class="pre">NULL</span></code>, the <em>Py_tp_base</em> slot is used instead.
If that also is <code class="docutils literal notranslate"><span class="pre">NULL</span></code>, the new type derives from <a class="reference internal" href="../library/functions.html#object" title="object"><code class="xref py py-class docutils literal notranslate"><span class="pre">object</span></code></a>.</p>
<p>This function calls <a class="reference internal" href="#c.PyType_Ready" title="PyType_Ready"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyType_Ready()</span></code></a> on the new type.</p>
<div class="versionadded">
<p><span class="versionmodified added">New in version 3.3.</span></p>
</div>
</dd></dl>

<dl class="function">
<dt id="c.PyType_FromSpec">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PyType_FromSpec</code><span class="sig-paren">(</span><a class="reference internal" href="#c.PyType_Spec" title="PyType_Spec">PyType_Spec</a><em> *spec</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyType_FromSpec" title="Permalink to this definition">¶</a></dt>
<dd><em class="refcount">Return value: New reference.</em><p>Equivalent to <code class="docutils literal notranslate"><span class="pre">PyType_FromSpecWithBases(spec,</span> <span class="pre">NULL)</span></code>.</p>
</dd></dl>

<dl class="type">
<dt id="c.PyType_Spec">
<code class="sig-name descname">PyType_Spec</code><a class="headerlink" href="#c.PyType_Spec" title="Permalink to this definition">¶</a></dt>
<dd><p>Structure defining a type’s behavior.</p>
<dl class="member">
<dt id="c.PyType_Spec.PyType_Spec.name">
const char* <code class="sig-name descname">PyType_Spec.name</code><a class="headerlink" href="#c.PyType_Spec.PyType_Spec.name" title="Permalink to this definition">¶</a></dt>
<dd><p>Name of the type, used to set <a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_name" title="PyTypeObject.tp_name"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyTypeObject.tp_name</span></code></a>.</p>
</dd></dl>

<dl class="member">
<dt id="c.PyType_Spec.PyType_Spec.basicsize">
int <code class="sig-name descname">PyType_Spec.basicsize</code><a class="headerlink" href="#c.PyType_Spec.PyType_Spec.basicsize" title="Permalink to this definition">¶</a></dt>
<dd></dd></dl>

<dl class="member">
<dt id="c.PyType_Spec.PyType_Spec.itemsize">
int <code class="sig-name descname">PyType_Spec.itemsize</code><a class="headerlink" href="#c.PyType_Spec.PyType_Spec.itemsize" title="Permalink to this definition">¶</a></dt>
<dd><p>Size of the instance in bytes, used to set
<a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_basicsize" title="PyTypeObject.tp_basicsize"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyTypeObject.tp_basicsize</span></code></a> and
<a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_itemsize" title="PyTypeObject.tp_itemsize"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyTypeObject.tp_itemsize</span></code></a>.</p>
</dd></dl>

<dl class="member">
<dt id="c.PyType_Spec.PyType_Spec.flags">
int <code class="sig-name descname">PyType_Spec.flags</code><a class="headerlink" href="#c.PyType_Spec.PyType_Spec.flags" title="Permalink to this definition">¶</a></dt>
<dd><p>Type flags, used to set <a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_flags" title="PyTypeObject.tp_flags"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyTypeObject.tp_flags</span></code></a>.</p>
<p>If the <code class="docutils literal notranslate"><span class="pre">Py_TPFLAGS_HEAPTYPE</span></code> flag is not set,
<a class="reference internal" href="#c.PyType_FromSpecWithBases" title="PyType_FromSpecWithBases"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyType_FromSpecWithBases()</span></code></a> sets it automatically.</p>
</dd></dl>

<dl class="member">
<dt id="c.PyType_Spec.PyType_Spec.slots">
<a class="reference internal" href="#c.PyType_Slot" title="PyType_Slot">PyType_Slot</a> *<code class="sig-name descname">PyType_Spec.slots</code><a class="headerlink" href="#c.PyType_Spec.PyType_Spec.slots" title="Permalink to this definition">¶</a></dt>
<dd><p>Array of <a class="reference internal" href="#c.PyType_Slot" title="PyType_Slot"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyType_Slot</span></code></a> structures.
Terminated by the special slot value <code class="docutils literal notranslate"><span class="pre">{0,</span> <span class="pre">NULL}</span></code>.</p>
</dd></dl>

</dd></dl>

<dl class="type">
<dt id="c.PyType_Slot">
<code class="sig-name descname">PyType_Slot</code><a class="headerlink" href="#c.PyType_Slot" title="Permalink to this definition">¶</a></dt>
<dd><p>Structure defining optional functionality of a type, containing a slot ID
and a value pointer.</p>
<dl class="member">
<dt id="c.PyType_Slot.PyType_Slot.slot">
int <code class="sig-name descname">PyType_Slot.slot</code><a class="headerlink" href="#c.PyType_Slot.PyType_Slot.slot" title="Permalink to this definition">¶</a></dt>
<dd><p>A slot ID.</p>
<p>Slot IDs are named like the field names of the structures
<a class="reference internal" href="#c.PyTypeObject" title="PyTypeObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyTypeObject</span></code></a>, <a class="reference internal" href="typeobj.html#c.PyNumberMethods" title="PyNumberMethods"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyNumberMethods</span></code></a>,
<a class="reference internal" href="typeobj.html#c.PySequenceMethods" title="PySequenceMethods"><code class="xref c c-type docutils literal notranslate"><span class="pre">PySequenceMethods</span></code></a>, <a class="reference internal" href="typeobj.html#c.PyMappingMethods" title="PyMappingMethods"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyMappingMethods</span></code></a> and
<a class="reference internal" href="typeobj.html#c.PyAsyncMethods" title="PyAsyncMethods"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyAsyncMethods</span></code></a> with an added <code class="docutils literal notranslate"><span class="pre">Py_</span></code> prefix.
For example, use:</p>
<ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">Py_tp_dealloc</span></code> to set <a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_dealloc" title="PyTypeObject.tp_dealloc"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyTypeObject.tp_dealloc</span></code></a></p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">Py_nb_add</span></code> to set <a class="reference internal" href="typeobj.html#c.PyNumberMethods.nb_add" title="PyNumberMethods.nb_add"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyNumberMethods.nb_add</span></code></a></p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">Py_sq_length</span></code> to set <a class="reference internal" href="typeobj.html#c.PySequenceMethods.sq_length" title="PySequenceMethods.sq_length"><code class="xref c c-member docutils literal notranslate"><span class="pre">PySequenceMethods.sq_length</span></code></a></p></li>
</ul>
<p>The following fields cannot be set using <a class="reference internal" href="#c.PyType_Spec" title="PyType_Spec"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyType_Spec</span></code></a> and <a class="reference internal" href="#c.PyType_Slot" title="PyType_Slot"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyType_Slot</span></code></a>:</p>
<ul class="simple">
<li><p><a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_dict" title="PyTypeObject.tp_dict"><code class="xref c c-member docutils literal notranslate"><span class="pre">tp_dict</span></code></a></p></li>
<li><p><a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_mro" title="PyTypeObject.tp_mro"><code class="xref c c-member docutils literal notranslate"><span class="pre">tp_mro</span></code></a></p></li>
<li><p><a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_cache" title="PyTypeObject.tp_cache"><code class="xref c c-member docutils literal notranslate"><span class="pre">tp_cache</span></code></a></p></li>
<li><p><a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_subclasses" title="PyTypeObject.tp_subclasses"><code class="xref c c-member docutils literal notranslate"><span class="pre">tp_subclasses</span></code></a></p></li>
<li><p><a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_weaklist" title="PyTypeObject.tp_weaklist"><code class="xref c c-member docutils literal notranslate"><span class="pre">tp_weaklist</span></code></a></p></li>
<li><p><code class="xref c c-member docutils literal notranslate"><span class="pre">tp_print</span></code></p></li>
<li><p><a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_weaklistoffset" title="PyTypeObject.tp_weaklistoffset"><code class="xref c c-member docutils literal notranslate"><span class="pre">tp_weaklistoffset</span></code></a></p></li>
<li><p><a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_dictoffset" title="PyTypeObject.tp_dictoffset"><code class="xref c c-member docutils literal notranslate"><span class="pre">tp_dictoffset</span></code></a></p></li>
<li><p><a class="reference internal" href="typeobj.html#c.PyBufferProcs.bf_getbuffer" title="PyBufferProcs.bf_getbuffer"><code class="xref c c-member docutils literal notranslate"><span class="pre">bf_getbuffer</span></code></a></p></li>
<li><p><a class="reference internal" href="typeobj.html#c.PyBufferProcs.bf_releasebuffer" title="PyBufferProcs.bf_releasebuffer"><code class="xref c c-member docutils literal notranslate"><span class="pre">bf_releasebuffer</span></code></a></p></li>
</ul>
<p>Setting <code class="xref c c-data docutils literal notranslate"><span class="pre">Py_tp_bases</span></code> or <code class="xref c c-data docutils literal notranslate"><span class="pre">Py_tp_base</span></code> may be
problematic on some platforms.
To avoid issues, use the <em>bases</em> argument of
<code class="xref py py-func docutils literal notranslate"><span class="pre">PyType_FromSpecWithBases()</span></code> instead.</p>
</dd></dl>

<dl class="member">
<dt id="c.PyType_Slot.PyType_Slot.pfunc">
void *<code class="sig-name descname">PyType_Slot.pfunc</code><a class="headerlink" href="#c.PyType_Slot.PyType_Slot.pfunc" title="Permalink to this definition">¶</a></dt>
<dd><p>The desired value of the slot. In most cases, this is a pointer
to a function.</p>
<p>May not be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
</dd></dl>

</dd></dl>

</div>
</div>


          </div>
        </div>
      </div>
      <div class="sphinxsidebar" role="navigation" aria-label="main navigation">
        <div class="sphinxsidebarwrapper">
  <h3><a href="../contents.html">Table of Contents</a></h3>
  <ul>
<li><a class="reference internal" href="#">Type Objects</a><ul>
<li><a class="reference internal" href="#creating-heap-allocated-types">Creating Heap-Allocated Types</a></li>
</ul>
</li>
</ul>

  <h4>Previous topic</h4>
  <p class="topless"><a href="concrete.html"
                        title="previous chapter">Concrete Objects Layer</a></p>
  <h4>Next topic</h4>
  <p class="topless"><a href="none.html"
                        title="next chapter">The <code class="docutils literal notranslate"><span class="pre">None</span></code> Object</a></p>
  <div role="note" aria-label="source link">
    <h3>This Page</h3>
    <ul class="this-page-menu">
      <li><a href="../bugs.html">Report a Bug</a></li>
      <li>
        <a href="https://github.com/python/cpython/blob/3.8/Doc/c-api/type.rst"
            rel="nofollow">Show Source
        </a>
      </li>
    </ul>
  </div>
        </div>
      </div>
      <div class="clearer"></div>
    </div>  
    <div class="related" role="navigation" aria-label="related navigation">
      <h3>Navigation</h3>
      <ul>
        <li class="right" style="margin-right: 10px">
          <a href="../genindex.html" title="General Index"
             >index</a></li>
        <li class="right" >
          <a href="../py-modindex.html" title="Python Module Index"
             >modules</a> |</li>
        <li class="right" >
          <a href="none.html" title="The None Object"
             >next</a> |</li>
        <li class="right" >
          <a href="concrete.html" title="Concrete Objects Layer"
             >previous</a> |</li>

          <li><img src="../_static/py.svg" alt="python logo" style="vertical-align: middle; margin-top: -1px"/></li>
          <li><a href="https://www.python.org/">Python</a> &#187;</li>
          <li class="switchers">
            <div class="language_switcher_placeholder"></div>
            <div class="version_switcher_placeholder"></div>
          </li>
          <li>
              
          </li>
    <li id="cpython-language-and-version">
      <a href="../index.html">3.8.13 Documentation</a> &#187;
    </li>

          <li class="nav-item nav-item-1"><a href="index.html" >Python/C API Reference Manual</a> &#187;</li>
          <li class="nav-item nav-item-2"><a href="concrete.html" >Concrete Objects Layer</a> &#187;</li>
                <li class="right">
                    

    <div class="inline-search" role="search">
        <form class="inline-search" action="../search.html" method="get">
          <input placeholder="Quick search" aria-label="Quick search" type="text" name="q" />
          <input type="submit" value="Go" />
          <input type="hidden" name="check_keywords" value="yes" />
          <input type="hidden" name="area" value="default" />
        </form>
    </div>
                     |
                </li>
            
      </ul>
    </div>  
    <div class="footer">
    &copy; <a href="../copyright.html">Copyright</a> 2001-2022, Python Software Foundation.
    <br />
    This page is licensed under the Python Software Foundation License Version 2.
    <br />
    Examples, recipes, and other code in the documentation are additionally licensed under the Zero Clause BSD License.
    <br />
    
    <br />

    The Python Software Foundation is a non-profit corporation.
<a href="https://www.python.org/psf/donations/">Please donate.</a>
<br />
    <br />

    Last updated on Mar 17, 2022.
    <a href="https://docs.python.org/3/bugs.html">Found a bug</a>?
    <br />

    Created using <a href="https://www.sphinx-doc.org/">Sphinx</a> 2.4.4.
    </div>

  </body>
</html>